A patellar clamp and saw guide are used during a total knee arthroplasty procedure to prepare the posterior surface of a patellar bone to accept a prosthetic implant.
Typically, a surgeon will select a patellar prosthesis for implantation either by utilizing a resurfacing technique wherein the prosthetic patella will be resected and resurfaced or by an insetting procedure where the patella is inserted into the prepared surface of the patella. Accordingly, two varieties of guides could be available for connection to the patellar clamp and could be interchangeably connectable to the clamp. The interchangeable guides permit a surgeon to use the patellar clamp during either a total patellar bone resurfacing procedure or a patella insetting procedure.
As used herein, when referring to bones or other parts of the body, the term “proximal” means closer to the heart and the term “distal” means more distant from the heart. The term “inferior” means toward the feet and the term “superior” means towards the head. The term “anterior” means towards the front part of the body or the face and the term “posterior” means towards the back of the body. The term “medial” means toward the midline of the body and the term “lateral” means away from the midline of the body.
In either a total resurfacing procedure or a patella insetting procedure, it is important that a sufficient amount of bone stock remain after resection to accept the fixation pegs of the patellar prosthesis and maintain the integrity of the remaining patellar bone. Therefore, proper location of the saw blade is important. Furthermore, surgical techniques for implanting knee prosthesis have been developed whereby the bone surfaces are prepared and the implants are inserted through relatively small incisions made medially or laterally on the knee. Such a technique is shown in U.S. Publication No. 2003/0171757. In this technique, a patella cutting guide which does not require everting the patella and which permits a lateral or medial approach for resecting the patella.
Prior art devices for aiding the surgeon in performing patella resections are well known to those skilled in the art. For example, Peterson, in U.S. Pat. No. 4,663,862, teaches a method and instruments for the installation of a patella button prosthesis which involves performing a patella resection.
In particular, Peterson relates to a saw guide which comprises a pliers-like instrument having a pair of mutually pivotable jaw members. The jaw members are designed so as to enable them to surround the outer periphery of the patella with each jaw member having a respective handle, integrally formed therewith, which handles may be pivoted so as to pivot the jaw members to and from engagement with the patella periphery. At the ends of the handles, a locking device is provided which enables the locking of the jaw members about the patella periphery. The Peterson device requires that a flat saw blade be guided over the face of the jaw members after the patella has been set to the correct depth between the members.
U.S. Pat. No. 5,147,365 relates to a patella osteotomy guide in which the jaw members include a slot for guiding the flat saw blade and an arm for setting the saw blade depth in the patella.
U.S. Pat. No. 5,486,177 relates to a patella milling instrument having a clamp which contacts the underside of the patella. A similar clamping tool is shown in U.S. Pat. No. 5,284,482.
U.S. Pat. No. 5,222,955 relates to a reaming system designed to cut a conical bore in a patella surface while the patella is being held in a patella clamp similar to that disclosed in U.S. Pat. No. 5,284,482.
U.S. Pat. No. 5,941,884, the teachings of which are incorporated herein by reference, relates to a patella clamp which includes indicia of both the amount of bone resected and the amount of bone remaining. The resection depth is set via a stop collar on a toothed extension. U.S. Pat. No. 5,441,884 does not provide any method of setting the depth of the patella milling based on the amount of bone remaining. U.S. Pat. No. 5,575,793 is similar in that a gage is provided to set the amount of bone to be removed.